The Cycloaddition Reaction of Isonitrile to Ketenimine Formed by the Reaction of Isonitrile with Carbene

Abstract

Abstract The reaction of several 2-, 4-, and/or 6-fnethyl-substituted phenylisonitrile with dihalocarbene and diphenylcarbene has been studied. The reaction of methyl-substituted phenylisonitrile with dihalocarbene gave indolenine or indoloquinoline derivatives via ketenimine intermediate which might be produced by α-addition of carbene to isonitrile. In contrast, the reaction of 2,6-dimethylphenylisonitrile with diphenylcarbene presumably formed by photolysis of diphenyldiazomethane gave N-(2,6-dimethylphenyl)diphenylketenimine, and further caused a cycloaddition reaction with isonitrile to yield indonimine derivatives. The structure of these products are discussed on the basis of the spectral data and chemical reactions. The mechanistic pathway of these reactions and the effect of methyl substituent in the cyclization stage are also discussed.